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At least 1,225 records · Page 68Linked to original sources
PubMed1993

Transcription initiation sites of prototype and variant JC virus early and late messenger RNAs.

The locations of the authentic viral transcription initiation sites utilized during the course of a JCV(Mad1) infection of primary human fetal glial (PHFG) cells have been identified using the S1 nuclease and primer extension techniques. Early viral mRNA start sites were located 20 to 30 nucleotides (positions 89-92 and 5115-5125) downstream from the two TATA elements present within the promoter-enhancer region of the JCV(Mad1) strain. Absence of the distal TATA element, as seen in the JCV(Mad4) promoter-enhancer, resulted in the alteration of the position and intensity of these sites. Several start sites were observed for late viral mRNAs; two sites were located 25 and 35 nucleotides (positions 191-192 and 200-203) downstream from a potential surrogate TATA signal. To determine whether the presence of constitutively expressed JCV large T protein would alter the pattern of transcription initiation, RNA isolated from JCV(Mad1)-infected POJ cells was analyzed. Although the positions of the early and late viral mRNA start sites were similar to those observed in JCV(Mad1)-infected PHFG cells, they were detected earlier in the course of the infection.

Bacteriophage M13↗
PubMed1994

A cell line that expresses a reporter gene in response to infection by Sindbis virus: a prototype for detection of positive strand RNA viruses.

We describe a stably transformed cell line (BHKSINLuc2) that contains a defective Sindbis virus genome under the control of a Rous sarcoma virus promoter and the luciferase gene downstream of the viral subgenomic RNA promoter. This cell line expresses high levels of luciferase activity following infection with Sindbis virus and provides a sensitive assay for titering variants of Sindbis virus that lack the structural protein genes, in particular, Sindbis virus replicons that express heterologous proteins. Cell lines such as this may be of value for detection of positive-strand RNA viruses.

Alphavirus↗
PubMed1998

Preliminary evaluation of a prototype spatially resolved spectrometer.

Near infrared spectroscopy (NIRS) has become an established research tool and is now being explored in several clinical settings [7]. However, until recently NIRS has not been fully quantified and changes have been difficult to interpret [4]. A new development by Hamamatsu Photonics, called the Spatially Resolved Spectrometer (SRS), proposes to be able to give a quantitative measure of oxygen saturation. We have incorporated the SRS into a multimodality monitoring system in three different clinical situations: 1) patients undergoing routine cardiopulmonary bypass, 2) head injured patients and 3) patients undergoing right-sided carotid endarterectomy. The importance of this investigation is in the development of the SRS machine which shows potential as a useful clinical tool. The results demonstrated good correlation between SRS and jugular venous oximetry (SjO2) in about 50% of patients. Although these results are encouraging, this study suggests that the SRS, in its present form, is not a reliable clinical monitor of cerebral oxygen saturation.

Brain↗
PubMed1990

Methylamine oxidase from Arthrobacter P1 as a prototype of eukaryotic plasma amine oxidase and diamine oxidase.

Methylamine oxidase (MAOx) from Gram-positive soil bacterium Arthrobacter P1 catalyzes the oxidation of CH3NH2 to H2C = O and NH4+ via reduction of O2 to H2O2. Past work indicates that MAOx is similar to mammalian plasma amine oxidase (PAO) and diamine oxidase (DAO), plant DAO, and yeast peroxisomal amine oxidase (YAO). All have Mr congruent to 170,000 and are composed of 2 identical subunits, each of which contains 1 atom of Cu(II) and one molecule of quinonoid cofactor. Herein, we report further evidence as to the striking similarity of these enzymes, and describe properties of MAOx which offer insights into understanding the eukaryotic oxidases. It is our belief that the structure of the quinone cofactor, and the Cu(II) site in MAOx are identical to these sites in PAO and DAO.

Amine Oxidase (Copper-Containing)↗
PubMed1986

Agonist and antagonist effects of prototype opiate drugs in fentanyl dose-dose discrimination.

The experiments characterized the effects of fentanyl, morphine, naloxone, cyclazocine, nalorphine, ketocyclazocine and N-allylnormetazocine in rats that were trained to discriminate 0.04 mg/kg from 0.02 mg/kg fentanyl (dose-dose discrimination). The data are compared to results obtained previously in rats discriminating 0.04 mg/kg fentanyl from saline (drug-saline discrimination). In the dose-dose discrimination fentanyl and morphine produced responding appropriate to 0.04 mg/kg fentanyl at doses which were 3.0- and 1.6-fold higher, respectively, than in drug-saline discrimination. Naloxone antagonized the stimulus effects of 0.04 mg/kg fentanyl at 9.8-fold lower doses than in drug-saline discrimination. The dose-effect curves of fentanyl and naloxone in rats discriminating 0.04 mg/kg from 0.02 mg/kg fentanyl, were steeper than in rats discriminating 0.04 mg/kg fentanyl from saline. While cyclazocine, nalorphine and N-allylnormetazocine acted as mixed and partial agonists/antagonists in drug-saline discrimination, those compounds acted as pure and complete antagonists of 0.04 mg/kg fentanyl in dose-dose discrimination. The rank order of compounds in antagonizing the stimulus effects of 0.04 mg/kg fentanyl in dose-dose discrimination was naloxone greater than N-allylnormetazocine greater than cyclazocine greater than nalorphine. It is suggested that a greater magnitude of opiate activity is required for producing generalization with the same 0.04 mg/kg dose of fentanyl in dose-dose as compared with drug-saline discrimination. Dose-dose discrimination may afford a more accurate method of the discriminative stimulus properties of drugs.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1979

Staphylococcal nuclease reviewed: a prototypic study in contemporary enzymology. IV. The nuclease as a model for protein folding.

This is the last in a series of four articles in which the chemical, enzymological and crystallographic work on Ribonucleate (deoxyribonucleate)-3'-nucleotidohydrolase, EC 3.1.4.4 (staphylococcal nuclease, micrococcal nuclease) will be reviewed and correlated. This article discusses the use of the nuclease as a model system for the study of the mechanisms and energetics of the folding-unfolding reaction in proteins and for the study of the interrelationships between amino acid sequence and three-dimensional structure.

Epitopes↗
PubMed1979

Staphylococcal nuclease reviewed: a prototypic study in contemporary enzymology. III. Correlation of the three-dimensional structure with the mechanisms of enzymatic action.

This is the third in a series of four articles in which the chemical, enzymological and crystallographic work on Ribonucleate (deoxribonucleate)-3'-nucleotidohydrolase, EC 3.1.4.4 (staphylococcal nuclease, micrococcal nuclease) will be reviewed and correlated. This article describes the structure of the nuclease and of a nuclease-inhibitor complex as determined by x-ray crystallography. The crystal structures are correlated with some of the known chemical and enzymological properties of the enzyme, and the three areas combined to propose a mechanism of action.

Amino Acid Sequence↗
PubMed1979

Staphylococcal nuclease reviewed: a prototypic study in contemporary enzymology. II. Solution studies of the nucleotide binding site and the effects of nucleotide binding.

This is the second of a series of four articles in which the chemical, enzymological and crystallographic work on Ribonucleate (deoxyribonucleate)-3'-nucleotidohydrolase, EC 3.1.4.4. (staphylococcal nuclease, micrococcal nuclease) will be reviewed and correlated. This article discusses studies in solution delineating the extent of the binding site of the enzyme and identifying some of the particular amino acid residues that form this site. In addition, the effects of the very potent inhibitory combination of thymidine-3',5'-diphosphate and Ca2+ on the conformation of the enzyme and its physical, chemical and enzymological properties will be reviewed.

Binding Sites↗
PubMed1979

The hepatitis B virus and its DNA polymerase: the prototype three-D virus.

The hepatitis B virus (HBV), the causal agent of serum hepatitis, has a diameter of 42 nm and is comprised of an outer surface coat and a 27 nm core. A unique DNA-dependent DNA polymerase is associated with the core of the virus. The core also houses a circular DNA that contains both double-stranded and single-stranded regions. In the endogenous reaction, the DNA polymerase repairs the single-stranded gaps of the viral DNA. The surface protein of the virus, called hepatitis B surface antigen, contains both lipid and carbohydrate, and is often present in particulate form in the blood of infected patients. In Asia and Africa HBV infection is associated with subsequent development of primary hepatocellular carcinoma. Although most patients recover completely from acute illness, the hepatitis B virus may cause chronic infection. Recently, a virus similar to human HBV was discovered in woodchucks. HBV has not yet been propagated in a cell culture system and the mode of replication of this unusual virus in hepatocytes is still moot. Although reliable therapy has not yet been provided, the problem of this world-wide infection has led to many interesting approaches to both vaccine production and anti-viral chemotherapy.

Animals↗
PubMed1975

Exclusion gene mapping utilizing patients with chromosome imbalance: the HL-A system as a prototype.

17 chromosomally unbalanced patients, their siblings and parents were tested for HL-A types and for up to 25 other polymorphic systems to determine whether there was gain or loss of an allele concurrent with the gain or loss of chromosome material. 5 patients had trisomy of part or all of a chromosome; 2 had trisomy of a segment and also deletion of chromosome material. All 7 were due to a familial translocation. The remaining patients had small deletions; 5 had ring chromosomes, 4 had rod deletions and 1 had missing chromosome material due to a heritable translocation. All cases were informative at the HL-A loci because of the high degree of polymorphism of the system whereas only some of the other systems were informative. None of the 17 patients showed unusual inheritance of HL-A or any other of the polymorphic systems examined. These results provide evidence excluding the HL-A and other loci from a number of possible locations in the human genome.

Blood Group Antigens↗
PubMed1980

Precise determination of protein antigenic structures has unravelled the molecular immune recognition of proteins and provided a prototype for synthetic mimicking of other protein binding sites.

Intensive research in the author's laboratory had culminated in the determination and synthesis of all the antigenic sites of myoglobin in 1975 and of lysozyme in 1978. Very recently most of the antigenic sites of serum albumin were also localized and synthesized. These investigations provided the first unique insight into the molecular features responsible for the immune recognition of protein antigens and of the factors which determine and regulate the antigenicity of the sites. But moreover, these studies have charted a multi-approach chemical strategy for investigation and synthetic duplication of protein binding sites. Furthermore, the concept of 'surface-simulation' synthesis, which we introduced and developed during our determination of the antigenic structure of lysozyme, has provided a remarkable dimension of unlimited versatility for the synthetic mimicking of any type of protein binding sites. In this concept, the spatially adjacent residues of a protein binding site are linked directly via peptide bonds with appropriate spacers into a single peptide which does not exist in the protein but mimicks a surface region of it. This has proved to be a powerful concept in protein molecular recognition and has opened up many untapped avenues in investigation, duplication and perhaps manipulation of a variety of protein activities. In fact, binding sites representing other protein activities (including antibody combining sites) have or are now being mimicked synthetically in our laboratory by the concept of surface-simulation synthesis.

Amino Acid Sequence↗
PubMed1982

Expression of beta-glucuronidase haplotypes in prototype and congenic mouse strains.

A gene complex consists of a structural gene with its associated regulatory information; together they behave as the functional and evolutionary unit of mammalian chromosomes. The use of congenic lines, in which alternate forms, or haplotypes, of a gene complex are transferred into a common genetic background by repeated backcrossing, provides a means of comparing the regulatory properties of different haplotypes of a gene complex without the complications introduced by extraneous genetic differences. We have now carried out such a study of the A, B, and H haplotypes of the beta-glucuronidase gene complex, [Gus], in mice. These haplotypes were derived from strains A/J, C57BL/6J, and C3H/HeJ and were compared against the C57BL/6J genetic background. Enzyme structure was compared in terms of charge (isoelectric point), stability (rate of thermal denaturation), substrate affinity (for 4 MU glucuronide), and antigenicity (reactivity with a standard antibody). Compared to the B form, the enzyme coded by the A haplotype has a lower isoelectric point, and that coded by the H haplotype is less stable. The decreased stability is the result of a lower activation energy for the thermal denaturation reaction. These differences were maintained in the congenic strains. All three enzyme forms showed identical substrate affinities. Antigenicity per enzyme unit was also identical for all three, indicating that none lacks an antigenic site possessed by the others and that they all possess the same catalytic activity per molecule. The expression of alleles of the Gus-t temporal locus within the gene complex was not affected by transfer into the C57BL/6 genetic background. The same developmental switches in enzyme activity were seen in each case. Transfer into the C57Bl/6 background also did not affect expression of the Gus-r regulator determining androgen inducibility of beta-glucuronidase synthesis in kidney epithelial cells. However, enzyme accumulation in induced cells was altered when the haplotypes were transferred into the C57BL/6 genetic background. Since the rate of synthesis was not affected, it suggests that the genetic differences between strains that are not linked to the [Gus] complex affect the rate of enzyme loss by degradation or secretion. Beta-Glucuronidase in liver is present in both lysosomes and endoplasmic reticulum (microsomes). The relative amount of enzyme at each site depended on both the indentity of the structural allele and the function of unlinked genetic modifiers. Within the C57BL/6 background the percentage of total enzyme present in the microsome fraction was the order A greater than B greater than H. For the H form of the enzyme the percentage was appreciably greater in the C3H genetic background compared to C57BL/6. As expected, then, the [Gus] complex contains all of the genetic determinants of enzyme structure detected by thermal stability and isoelectric point measurements...

Animals↗